U.S. patent number 7,521,269 [Application Number 11/503,720] was granted by the patent office on 2009-04-21 for single-crystal nitride-based semiconductor substrate and method of manufacturing high-quality nitride-based light emitting device by using the same.
This patent grant is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to June-O Song.
United States Patent |
7,521,269 |
Song |
April 21, 2009 |
Single-crystal nitride-based semiconductor substrate and method of
manufacturing high-quality nitride-based light emitting device by
using the same
Abstract
A nitride-based light emitting device is manufactured by using a
single-crystal nitride-based semiconductor substrate. A seed
material layer is deposited on a first substrate where organic
residues including a natural oxide layer are removed from an upper
surface of the first substrate. A multifunctional substrate is
grown from the seed material layer. The single-crystal
nitride-based semiconductor layer including a nitride-based buffer
layer is formed on the multifunctional substrate. The seed material
layer primarily assists the growth of the multifunctional
substrate, which is essentially required for the growth of the
single-crystal nitride-based semiconductor substrate. The
multifunctional substrate is prepared in the form of a
single-crystal layer or a poly-crystal layer having a hexagonal
crystalline structure. The light emitting device employing the
single-crystal nitride-based semiconductor substrate is used as a
next-generation white light source having high capacity, large
area, high brightness and high performance.
Inventors: |
Song; June-O (Yongin-si,
KR) |
Assignee: |
Samsung Electronics Co., Ltd.
(KR)
|
Family
ID: |
37271545 |
Appl.
No.: |
11/503,720 |
Filed: |
August 14, 2006 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20070034892 A1 |
Feb 15, 2007 |
|
Foreign Application Priority Data
|
|
|
|
|
Aug 12, 2005 [KR] |
|
|
10-2005-0074100 |
|
Current U.S.
Class: |
438/22; 257/103;
257/E21.104; 257/E33.025; 438/37; 438/47 |
Current CPC
Class: |
H01L
33/0075 (20130101); H01L 33/12 (20130101) |
Current International
Class: |
H01L
21/00 (20060101) |
Field of
Search: |
;438/22
;257/E33.002 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2001168389 |
|
Jun 2001 |
|
JP |
|
1020050058954 |
|
Jun 2005 |
|
KR |
|
Primary Examiner: Ho; Tu-Tu V
Attorney, Agent or Firm: Cantor Colburn LLP
Claims
What is claimed is:
1. A method of growing a single-crystal nitride-based semiconductor
substrate, the method comprising: depositing a seed material layer
on an upper surface of a first substrate and growing a
multifunctional substrate from an upper surface of the seed
material layer; forming a multi-layer on an upper surface of the
multifunctional substrate by (metal-organic chemical vapor
deposition) MOCVD, in which the multi-layer consists of a
nitride-based buffer layer and a single-crystal nitride-based layer
stacked on the nitride-based buffer layer; removing the seed
material layer, and the first substrate by performing wet etching
or dry etching; and performing a heat-treatment process in order to
enhance crystallinity of the multifunctional substrate and the
single-crystal nitride-based layer obtained through the above
steps.
2. The method of claim 1, wherein the first substrate includes
sapphire, silicon (Si), zinc oxide (ZnO) or gallium arsenide
(GaAs).
3. The method of claim 1, further comprising forming a ZnO-based
layer between the first substrate and the seed material layer,
wherein the ZnO-based layer is removed with the seed material layer
and the first substrate.
4. The method of claim 1, wherein the heat-treatment is performed
at a temperature of 1500.degree. C. or less under oxygen (O.sub.2),
nitrogen (N.sub.2), hydrogen (H.sub.2), argon (Ar), or air
atmosphere.
5. The method of claim 1, wherein a sequence of a manufacturing
procedure for the nitride-based light emitting device is
changeable.
6. A method of manufacturing a nitride-based light emitting device,
the method comprising: depositing a seed material layer on an upper
surface of a first substrate and growing a multifunctional
substrate from an upper surface of the seed material layer; forming
a multi-layer on an upper surface of the multifunctional substrate
by (metal-organic chemical vapor deposition) MOCVD, in which the
multi-layer consists of a nitride-based buffer layer, and a
single-crystal nitride-based layer including an n-nitride-based
cladding layer a nitride-based active layer, and a p-nitride-based
cladding layer, which are sequentially stacked on the upper surface
of the multifunctional substrate; removing the seed material layer,
and the first substrate by performing wet etching or dry etching;
performing a heat-treatment process in order to enhance
crystallinity of the multifunctional substrate and the multi-layer
obtained through the above steps; and selectively depositing
reflective electrode materials or transparent electrode materials
on the multi-layer having the multifunctional substrate and then
performing an ohmic heat-treatment process.
7. The method of claim 6, wherein the first substrate includes
sapphire, silicon (Si), zinc oxide (ZnO) or gallium arsenide
(GaAs).
8. The method of claim 6, further comprising forming a ZnO-based
layer between the first substrate and the seed material layer,
wherein the ZnO-based layer is removed with the seed material layer
and the first substrate.
9. The method of claim 6, wherein the heat-treatment is performed
at a temperature of 1500.degree. C. or less under oxygen (O.sub.2),
nitrogen (N.sub.2), hydrogen (H.sub.2), argon (Ar), or air
atmosphere.
10. The method of claim 6, wherein a sequence of a manufacturing
procedure for the nitride-based light emitting device is
changeable.
Description
This application claims priority to Korean Patent Application No.
2005-74100, filed on Aug. 12, 2005, and all the benefits accruing
therefrom under 35 U.S.C. .sctn. 119, the contents of which in its
entirety are herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a single-crystal nitride-based
semiconductor substrate and a method of manufacturing a vertical
type nitride-based light emitting device by using the same. More
particularly, the present invention relates to a method of growing
a single-crystal nitride-based semiconductor substrate under high
temperature and hydrogen atmosphere by using a seed material layer
("SML") and a multifunctional substrate ("MS"), which are
sequentially formed on an upper surface of a first substrate ("FS")
so as to prevent mechanical and thermal strain and decomposition
from occurring at the upper surface of the first substrate
including sapphire, silicon (Si), zinc oxide ("ZnO") or gallium
arsenide ("GaAs"). The present invention also relates to a
high-quality nitride-based light emitting device and a
manufacturing method thereof, in which the nitride-based light
emitting device employs a single-crystal nitride-based
semiconductor substrate and a light emitting structure, so that the
nitride-based light emitting device has a large size and represents
superior light efficiency and heat dissipation while being operated
at a low operational voltage.
2. Description of the Related Art
With the rapid technological advance of optoelectronic devices,
such as blue/green diodes, (near) infrared light emitting diodes,
laser diodes and optical sensors, single-crystal nitride-based
semiconductors have become very important materials in optical
industrial fields. In general, optoelectronic devices employing the
single-crystal nitride-based semiconductors are grown from the
upper surface of a thick insulating sapphire substrate or a
conductive silicon carbide ("SiC") substrate under the hydrogen
atmosphere where ammonium ("NH.sub.3") and hydrogen ("H.sub.2")
carrier gas are provided in a high temperature condition of
1200.degree. C. or more. However, since the insulating sapphire
substrate or the conductive silicon carbide substrate is expensive
as compared with a silicon substrate, the insulating sapphire
substrate and the conductive silicon carbide substrate are
inefficient for cost purposes. Since the nitride-based
optoelectronic devices generate a large amount of heat during the
operation thereof, the substrate must dissipate the heat generated
from the nitride-based optoelectronic devices. However, if the
nitride-based optoelectronic devices are formed on the upper
surface of the insulating sapphire substrate having a thickness of
70 micron meters or more, the insulating sapphire substrate cannot
easily dissipate the heat because the insulating sapphire substrate
has inferior thermal conductivity. Therefore, the insulating
sapphire substrate may not serve as a next-generation white light
source.
Different from the thick insulating sapphire substrate and the
silicon carbide substrate, a transparent conductive zinc oxide
("ZnO") substrate has a small difference in a lattice constant
relative to the nitride-based semiconductor while representing
superior electrical and thermal conductivities and higher light
transmittance. In addition, the transparent ZnO substrate can be
fabricated at an inexpensive cost., Therefore, the transparent ZnO
substrate has been recently spotlighted as a next-generation
substrate for the nitride-based light emitting devices. However,
the surface of the transparent conductive zinc oxide ("ZnO")
substrate becomes unstable under a high temperature of 600.degree.
C. or more and a high vacuum of 10.sup.-3 torr or more, thus easily
decomposing the materials of the transparent conductive zinc oxide
(ZnO) substrate. In addition, reduction of the transparent
conductive ZnO substrate is promoted in reducing ambient employment
of ammonium ("NH.sub.3") and hydrogen ("H.sub.2"). For this reason,
the single-crystal nitride-based semiconductor is rarely grown
under the reducing ambient having a temperature of 800.degree. C.
or more.
Other conductive substrates, including silicon (Si), silicon
germanium ("SiGe"), or gallium arsenide ("GaAs"), have been
suggested. However, these conductive substrates also represent
problems at a temperature of 500.degree. C. or more due to the
motion of the dislocation slip system provided in the conductive
substrates, thereby causing strain to and decomposition of
materials. In addition, since these conductive substrates represent
large differences in lattice constant and thermal expansion
coefficient relative to the nitride-based semiconductor,
high-quality nitride-based layers may not be easily grown from the
above conductive substrates.
A laser lift off ("LLO") method has been most recently spotlighted
in the industrial field as a method of manufacturing a
nitride-based light emitting device for a next-generation
high-brightness white light source. According to the LLO method, a
high-quality nitride-based semiconductor layer or a light emitting
structure is grown from an upper surface of a sapphire substrate
having inferior thermal and electrical conductivities, and then a
strong energy laser beam is irradiated onto a rear surface of the
sapphire substrate, thereby separating the nitride semiconductor
layer and the light emitting structure from the sapphire substrate.
A highly reliable nitride-based light emitting device representing
high brightness and having a large size required for the
next-generation white light source can be manufactured by using the
LLO method. However, since a strong energy laser beam is applied to
the sapphire substrate in order to separate the nitride-based
semiconductor layer and the light emitting structure from the
sapphire substrate, heat having a temperature of 900.degree. C. or
more is generated from the interfacial surface between the sapphire
substrate and the nitride-based semiconductor layer/the light
emitting structure, so that the nitride-based semiconductor layer
may be damaged or deformed, lowering the product yield and causing
difficulties during the manufacturing process.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a single-crystal nitride-based
semiconductor substrate and a method of manufacturing a vertical
type nitride-based light emitting device by using the same. More
particularly, the present invention provides a method of growing a
single-crystal nitride-based semiconductor substrate under the
high-temperature hydrogen atmosphere by using a seed material layer
SML and a multifunctional substrate MS, which are sequentially
formed on an upper surface of a first substrate FS so as to prevent
the upper surface of the first substrate including sapphire,
silicon (Si), zinc oxide (ZnO) or gallium arsenide (GaAs) from
being subject to mechanical and thermal strain and decomposition.
The present invention also provides a high-quality nitride-based
light emitting device and a manufacturing method thereof, in which
the nitride-based light emitting device employs a single-crystal
nitride-based semiconductor substrate and a light emitting
structure, so that the nitride-based light emitting device has a
large size and represents superior light efficiency and heat
dissipation while being operated at a low operational voltage.
In one aspect of the present invention, a seed material layer SML
is deposited on a first substrate FS where organic residues
including a natural oxide layer are removed from an upper surface
of the first substrate, and a multifunctional substrate MS is grown
from the seed material layer. A single-crystal nitride-based
semiconductor layer including a nitride-based buffer layer is
formed on the multifunctional substrate MS. The seed material layer
SML primarily assists the growth of the multifunctional substrate
MS, which is essentially required for the growth of the
single-crystal nitride-based semiconductor substrate as well as for
the fabrication of the highly reliable nitride-based light emitting
device employing the single-crystal nitride-based semiconductor
layer and the light emitting structure. In addition, the seed
material layer SML improves the product yield of the nitride-based
light emitting devices. In order to prevent the seed material layer
SML from being subjected to strain and decomposition under the
high-temperature hydrogen atmosphere, the multifunctional substrate
MS includes aluminum oxide ("Al--O"), aluminum nitride ("Al--N"),
aluminum nitride oxide ("Al--N--O"), gallium nitride ("Ga--N"),
boron nitride ("B--N"), silicon carbide ("Si--C"), or silicon
carbon nitride ("Si--C--N"). In addition, the multifunctional
substrate MS has a single crystal structure or a poly-crystal
structure to grow the single-crystal nitride-based semiconductor
layer having high quality. The single-crystal nitride-based
semiconductor substrate and the light emitting device using the
same can be used as a next-generation white light source having
high capacity, large area, high brightness and high
performance.
According to an exemplary embodiment of the present invention, the
single-crystal nitride-based semiconductor layer formed on the
multifunctional substrate MS including aluminum oxide ("Al--O"),
aluminum nitride ("Al--N"), aluminum nitride oxide ("Al--N--O"),
gallium nitride ("Ga--N"), boron nitride ("B--N"), silicon carbide
("Si--C"), or silicon carbon nitride ("Si--C--N") serves to provide
high-quality nitride-based optoelectronic devices and high-quality
nitride-based flip chip type light emitting devices. In particular,
the nitride-based light emitting devices include a nitride-based
light emitting structure, wherein the nitride-based light emitting
structure consists of a nitride-based buffer layer in the form of
an amorphous layer, a poly-crystal layer or a single-crystal layer
comprised of aluminum-indium-gallium-nitride (AlxInyGazN, wherein
x, y and z are integers), an n-nitride-based cladding layer
comprised of aluminum-indium-gallium-nitride (AlxInyGazN, wherein
x, y and z are integers), a p-nitride-based cladding layer
comprised of aluminum-indium-gallium-nitride (AlxInyGazN, wherein
x, y and z are integers) and a nitride-based active layer formed
between two nitride-based cladding layers and comprised of
aluminum-indium-gallium-nitride (AlxInyGazN, wherein x, y and z are
integers).
The multifunctional substrate MS, which is a primary element of the
present invention, includes at least one selected from the group
consisting of aluminum oxide ("Al--O"), aluminum nitride ("Al--N"),
aluminum nitride oxide ("Al--N--O"), gallium nitride ("Ga--N"),
boron nitride ("B--N"), silicon carbide ("Si--C") and silicon
carbon nitride ("Si--C--N"). In addition, the multifunctional
substrate MS has thermal stability and reduction-resistant
characteristics under the reduction atmosphere where ammonium
("NH.sub.3") and hydrogen ("H.sub.2") carrier gas are provided in
the high temperature condition of about 1100.degree. C. or more.
Further, the multifunctional substrate MS allows the single-crystal
nitride-based layer to be grown with a low density of dislocation
that exerts bad influence upon the electrical and electronic
characteristics of the optoelectronic device.
More preferably, the multifunctional substrate MS including
aluminum oxide ("Al--O"), aluminum nitride ("Al--N"), aluminum
nitride oxide ("Al--N--O"), gallium nitride ("Ga--N"), boron
nitride ("B--N"), silicon carbide ("Si--C"), or silicon carbon
nitride ("Si--C--N") is prepared in the form of a single crystal
layer or a poly-crystal layer having a hexagonal crystalline
structure. However, the present invention is not limited to the
above crystal structure.
In exemplary embodiments, at least one of silicon (Si), germanium
(Ge), indium (In), lithium (Li), gallium (Ga), magnesium (Mg), zinc
(Zn), beryllium (Be), molybdenum (Mo), vanadium (V), copper (Cu),
iridium (Ir), rhodium (Rh), ruthenium (Ru), tungsten (W), cobalt
(Co), nickel (Ni), manganese (Mn), titanium (Ti), tantalum (Ta),
chrome (Cr), and lanthanum (La) is added to the multifunctional
substrate MS including aluminum oxide ("Al--O"), aluminum nitride
("Al--N"), aluminum nitride oxide ("Al--N--O"), gallium nitride
("Ga--N"), boron nitride ("B--N"), silicon carbide ("Si--C"), or
silicon carbon nitride ("Si--C--N") in order to adjust
crystallinity and electron concentration and to reduce, as much as
possible, dislocation density in the single-crystal nitride-based
semiconductor layer formed on the upper surface of the
multifunctional substrate MS. In exemplary embodiments, the metal,
metal oxide, or metallic nitride oxide added to the multifunctional
substrate MS has a nano-phase such that the dislocation density in
the single-crystal nitride-based semiconductor layer can be easily
adjusted.
In exemplary embodiments, the amount of elements added to the
multifunctional substrate MS is limited within a range between 0.1
weight percent to 49 weight percent.
In exemplary embodiments, the multifunctional substrate MS has a
thickness of 20 micron meters or less.
In exemplary embodiments, the multifunctional substrate MS
including aluminum oxide ("Al--O"), aluminum nitride ("Al--N"),
aluminum nitride oxide ("Al--N--O"), gallium nitride ("Ga--N"),
boron nitride ("B--N"), silicon carbide ("Si--C"), or silicon
carbon nitride ("Si--C--N") is formed through high-temperature/low
temperature chemical vapor deposition ("CVD") using chemical
reaction and/or physical vapor deposition ("PVD"), wherein the CVD
includes metal-organic chemical vapor deposition ("MOCVD") and
plasma enhanced vapor deposition ("PECVD"), and the PVD includes
thermal or E-beam evaporation, pulsed laser deposition, sputtering
deposition employing gas ions, such as oxygen (O.sub.2), nitrogen
(N.sub.2), or argon (Ar), and co-sputtering deposition using at
least two sputtering guns.
More preferably, the multifunctional substrate MS is grown from the
upper surface of the seed material layer SML, which is formed on
the upper surface of the first substrate FS, within a temperature
range between room temperature and about 1500.degree. C.
In order to successively grow the multifunctional substrate MS
having superior crystallinity, the seed material layer SML is
primarily formed on the first substrate FS before the
multifunctional substrate MS is formed on the first substrate
FS.
The seed material layer SML is stacked on the upper surface of the
first substrate FS and allows the multifunctional substrate MS to
have superior crystallinity and the hexagonal crystalline
structure.
In exemplary embodiments, the seed material layer SML includes
metal, oxide, nitride, carbide, boride, oxynitride, carbonnitride,
or silicide as described below. In addition, the seed material
layer SML is prepared in the form of a single layer or a
multi-layer and has a thickness of 10 microns or less.
Examples of the metal used for the seed material layer 110 include:
Ti, Si, W, Co, Ni, Mo, Sc, Mg, Ge, Cu, Be, Zr, Fe, Al, Cr, Nb, Re,
Rh, Ru, Hf, Ir, Os, V, Pd, Y, Ta, Tc, La and rare-earth metals.
Examples of the oxide used for the seed material layer 110 include:
BeO, CeO.sub.2, Cr.sub.2O.sub.3, HfO.sub.2, La.sub.2O.sub.3, MgO,
Nb.sub.2O.sub.3, SiO.sub.2, Ta.sub.2O.sub.5, ThO.sub.2, TiO.sub.2,
Y.sub.2O.sub.3, ZrO.sub.2 and ZrSiO.sub.2,
Examples of the nitride used for the seed material layer 110
include: AlN, GaN, InN, BN, Be.sub.3N.sub.2, Cr.sub.2N, HfN, MoN,
NbN, Si.sub.3N.sub.4, TaN, Ta.sub.2N, Th.sub.2N.sub.2, TiN,
WN.sub.2, W.sub.2N, VN and ZrN.
Examples of the carbide used for the seed material layer 110
include: B.sub.4C, Cr.sub.2, HfC, LaC.sub.2, Mo.sub.2C, Nb.sub.2C,
SiC, Ta.sub.2C, ThC.sub.2, TiC, W.sub.2C, WC, V.sub.2C and ZrC,
Examples of the boride used for the seed material layer 110
include: AlB.sub.2, BeB.sub.2, CrB.sub.2, HfB.sub.2, LaB.sub.2,
MoB.sub.2, MoB, NbB.sub.4, SiB.sub.6, TaB.sub.2, ThB.sub.4,
TiB.sub.2, WB, VB.sub.2 and ZrB.sub.2.
Examples of the oxynitride used for the seed material layer 110
include AlON and SiON.
Examples of the carbonnitride used for the seed material layer 110
include SiCN,
Examples of the silicide used for the seed material layer 110
include: CrSi.sub.2, Cr.sub.2Si, HfSi.sub.2, MoSi.sub.2,
NbSi.sub.2, TaSi.sub.2, Ta.sub.5Si.sub.3, ThSi.sub.2,
Ti.sub.5Si.sub.3, WSi.sub.2, W.sub.5Si.sub.3, V.sub.3Si and
ZrSi.sub.2.
In exemplary embodiments, the seed material layer SML is formed
through high-temperature/low temperature chemical vapor deposition
("CVD") using chemical reaction and/or physical vapor deposition
("PVD"), wherein the CVD includes metal-organic chemical vapor
deposition ("MOCVD") and plasma enhanced vapor deposition
("PECVD"), and the PVD includes thermal or E-beam evaporation,
pulsed laser deposition, sputtering deposition employing gas ions,
such as oxygen (O.sub.2), nitrogen (N.sub.2), or argon (Ar), and
co-sputtering deposition using at least two sputtering guns.
More preferably, the seed material layer SML is deposited on the
upper surface of the first substrate within a temperature range
between room temperature and about 1500.degree. C.
In another exemplary embodiment of the present invention, a method
of growing the single-crystal nitride-based semiconductor substrate
includes;
depositing a seed material layer SML on an upper surface of a first
substrate FS including sapphire, silicon (Si), zinc oxide ("ZnO")
or gallium arsenide ("GaAs") and growing a multifunctional
substrate MS from an upper surface of the seed material layer
SML;
forming a multi-layer on an upper surface of the multifunctional
substrate MS by MOCVD (metal-organic chemical vapor deposition), in
which the multi-layer consists of a nitride-based buffer layer and
a thick single-crystal nitride-based layer stacked on the
nitride-based buffer layer;
removing the seed material layer SML, and the first substrate FS by
performing wet etching or dry etching; and
performing a heat-treatment process in order to enhance
crystallinity of the multifunctional substrate MS and the
single-crystal nitride-based layer obtained through the above
process.
In exemplary embodiments, further comprising forming a ZnO-based
layer between the first substrate FS and the seed material layer
SML, wherein the ZnO-based layer is removed with the seed material
layer SML and the first substrate FS.
In still another exemplary embodiment of the present invention, a
method of manufacturing a nitride-based light emitting device by
using a single-crystal nitride-based semiconductor substrate
includes:
depositing a seed material layer SML on an upper surface of a first
substrate FS including sapphire, silicon (Si), zinc oxide ("ZnO")
or gallium arsenide ("GaAs") and growing a multifunctional
substrate MS from an upper surface of the seed material layer
SML;
forming a multi-layer on an upper surface of the multifunctional
substrate MS by MOCVD, in which the multi-layer consists of a
nitride-based buffer layer, an n-nitride-based cladding layer, a
nitride-based active layer, and a p-nitride-based cladding layer,
which are sequentially stacked on the upper surface of the
multifunctional substrate MS;
removing the seed material layer SML, and the first substrate FS by
performing wet etching or dry etching;
performing a heat-treatment process in order to enhance
crystallinity of the multifunctional substrate MS and the
multi-layer obtained through the above process; and
selectively depositing reflective electrode materials or
transparent electrode materials on the multi-layer having the
multifunctional substrate MS and then performing an ohmic
heat-treatment process.
In exemplary embodiments, further comprising forming a ZnO-based
layer between the first substrate FS and the seed material layer
SML, wherein the ZnO-based layer is removed with the seed material
layer SML and the first substrate FS.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features and advantages of the present
invention will become readily apparent by reference to the
following detailed description when considered in conjunction with
the accompanying drawings wherein:
FIGS. 1A and 1B are cross-sectional views showing a seed material
layer in the form of a single layer or a bi-layer provided on an
upper surface of a first substrate, a multifunctional substrate
formed on the seed material layer, and a single-crystal
nitride-based layer (or a light emitting structure for a light
emitting device) formed on the multifunctional substrate for the
purpose of homoepitaxial growth;
FIGS. 2A and 2B are cross-sectional views showing a ZnO-based layer
formed on a first substrate, a seed material layer in the form of a
single layer or a bi-layer provided on an upper surface the
ZnO-based layer, a multifunctional substrate formed on the seed
material layer, and a single-crystal nitride-based layer (or a
light emitting structure for a light emitting device) formed on the
multifunctional substrate for the purpose of homoepitaxial
growth;
FIG. 3 is a cross-sectional view showing a stacked structure in
which a ZnO-based layer and the seed material layer have been
removed;
FIGS. 4A and 4B are a flowchart and a cross-sectional view showing
a vertical top emission type nitride-based light emitting device
fabricated by using a ZnO-based layer, a seed material layer and a
multifunctional substrate according to an exemplary embodiment of
the present invention;
FIGS. 5A and 5B are a flowchart and a cross-sectional view showing
a vertical flip chip type nitride-based light emitting device
fabricated by using a ZnO-based layer, a seed material layer and a
multifunctional substrate according to another exemplary embodiment
of the present invention; and
FIGS. 6A and 6B are a flowchart and a cross-sectional view showing
a vertical top emission type nitride-based light emitting device
fabricated by using a ZnO-based layer, a seed material layer and a
multifunctional substrate according to yet another exemplary
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the exemplary embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings. However, the present invention is not
limited to the exemplary embodiments illustrated hereinafter, and
the exemplary embodiments herein are rather introduced to provide
easy and complete understanding of the scope and spirit of the
present invention. Therefore, the present invention should not be
construed as being limited to the exemplary embodiments set forth
herein. Like reference numerals in the drawings denote like
elements.
The terminology used herein is for the purpose of describing
particular exemplary embodiments only and is not intended to be
limiting of the present invention. As used herein, the singular
forms, "a", "an" and "the" are intended to include the plural forms
as well, unless the context clearly indicates otherwise. It will be
further understood that the terms "includes" and/or "including",
when used in this specification, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof.
Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which the present
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
Hereinafter, a method of manufacturing a single-crystal
nitride-based semiconductor substrate by forming a ZnO-based layer,
a seed material layer ("SML") and a multifunctional substrate
("MS") on an upper surface of a first substrate ("FS") including
sapphire, silicon (Si), zinc oxide ("ZnO") or gallium arsenide
("GaAs"), and a method of manufacturing a high-quality
nitride-based optoelectronic device by using the single-crystal
nitride-based semiconductor substrate will be described with
reference to the accompanying drawings.
FIGS. 1A and 1B are cross-sectional views showing a seed material
layer ("SML") in the form of a single layer or a bi-layer provided
on an upper surface a first substrate ("FS"), a multifunctional
substrate ("MS") formed on the seed material layer SML, and a
single-crystal nitride-based layer (or a light emitting structure
for a light emitting device) formed on the multifunctional
substrate for the purpose of homoepitaxial growth.
Referring to FIG. 1A, a seed material layer 110 and a
multifunctional substrate 120 are sequentially formed on an upper
surface of a first substrate 100 including sapphire, silicon (Si),
zinc oxide ("ZnO") or gallium arsenide ("GaAs"). Then, a
single-crystal nitride-based layer or a light emitting structure
130 is grown from the upper surface of the multifunctional
substrate 120 in a metal organic vapor deposition ("MOCVD") chamber
under a hydrogen atmosphere where ammonium ("NH.sub.3") and
hydrogen ("H.sub.2") carrier gas are provided in a high temperature
condition of 1000.degree. C. or more.
The multifunctional substrate 120 is a primary element of the
present invention and includes at least one selected from the group
consisting of aluminum oxide ("Al--O"), aluminum nitride ("Al--N"),
aluminum nitride oxide ("Al--N--O"), gallium nitride ("Ga--N"),
boron nitride ("B--N"), silicon carbide ("Si--C"), and silicon
carbon nitride ("Si--C--N"), which has thermal stability and
reduction-resistant characteristics under the reduction atmosphere
where ammonium ("NH.sub.3") and hydrogen ("H.sub.2") carrier gas
are provided in a high temperature condition of 1000.degree. C. or
more.
In exemplary embodiments, the multifunctional substrate 120
including aluminum oxide ("Al--O"), aluminum nitride ("Al--N"),
aluminum nitride oxide ("Al--N--O"), gallium nitride ("Ga--N"),
boron nitride ("B--N"), silicon carbide ("Si--C"), or silicon
carbon nitride ("Si--C--N") is prepared in the form of a single
crystal layer or a poly-crystal layer having a hexagonal
crystalline structure. However, the present invention is not
limited to the above crystal structure.
In exemplary embodiments, oxide or nitride including at least one
of silicon (Si), germanium (Ge), indium (In), lithium (Li), gallium
(Ga), magnesium (Mg), zinc (Zn), beryllium (Be), molybdenum (Mo),
vanadium (V), copper (Cu), iridium (Ir), rhodium (Rh), ruthenium
(Ru), tungsten (W), cobalt (Co), nickel (Ni), manganese (Mn),
titanium (Ti), tantalum (Ta), chrome (Cr), and lanthanum (La) is
added to the multifunctional substrate 120 including aluminum oxide
("Al--O"), aluminum nitride ("Al--N"), aluminum nitride oxide
("Al--N--O"), gallium nitride ("Ga--N"), boron nitride ("B--N"),
silicon carbide ("Si--C"), or silicon carbon nitride ("Si--C--N")
in order to adjust crystallinity and electron concentration and to
reduce, as much as possible, dislocation density in the
single-crystal nitride-based semiconductor layer formed on the
upper surface of the multifunctional substrate 120. Preferably,
metal oxide or nitride oxide added to the multifunctional substrate
120 has a nano-phase such that the dislocation density in the
single-crystal nitride-based semiconductor layer can be easily
adjusted.
In exemplary embodiments, the amount of elements added to the
multifunctional substrate 120 is limited within a range of about
0.1 weight percent to about 49 weight percent.
In exemplary embodiments, the multifunctional substrate 120 has a
thickness of about 20 micron meters or less.
In exemplary embodiments, the multifunctional substrate 120
including aluminum oxide ("Al--O"), aluminum nitride ("Al--N"),
aluminum nitride oxide ("Al--N--O"), gallium nitride ("Ga--N"),
boron nitride ("B--N"), silicon carbide ("Si--C"), or silicon
carbon nitride ("Si--C--N") is formed through high-temperature/low
temperature chemical vapor deposition ("CVD") using chemical
reaction and/or physical vapor deposition ("PVD"), wherein the CVD
includes metal-organic chemical vapor deposition ("MOCVD") and
plasma enhanced chemical vapor deposition ("PECVD"), and the PVD
includes thermal or E-beam evaporation, pulsed laser deposition,
sputtering deposition employing gas ions, such as oxygen (O.sub.2),
nitrogen (N.sub.2), or argon (Ar), and co-sputtering deposition
using at least two sputtering guns.
More preferably, the multifunctional substrate 120 is grown from
the upper surface of the seed material layer 110, which is formed
on the upper surface of the first substrate 100, within a
temperature range between room temperature and 1500.degree. C.
In order to successively grow the multifunctional substrate 120
having superior crystallinity, the seed material layer 110 is
primarily formed on the first substrate 100 before the
multifunctional substrate 120 is formed on the first substrate
100.
The seed material layer 110 is stacked on the upper surface of the
first substrate 100 and allows the multifunctional substrate 120 to
have superior crystallinity and a hexagonal crystalline
structure.
In exemplary embodiments, the seed material layer 110 includes
metal, oxide, nitride, carbide, boride, oxynitride, carbonnitride,
or silicide as described below. In addition, the seed material
layer 110 is prepared in the form of a single layer or a
multi-layer having a thickness of 10 microns or less.
Examples of the metal used for the seed material layer 110 include:
Ti, Si, W, Co, Ni, Mo, Sc, Mg, Ge, Cu, Be, Zr, Fe, Al, Cr, Nb, Re,
Rh, Ru, Hf, Ir, Os, V, Pd, Y, Ta, Tc, La and rare-earth metals.
Examples of the oxide used for the seed material layer 110 include:
BeO, CeO.sub.2, Cr.sub.2O.sub.3, HfO.sub.2, La.sub.2O.sub.3, MgO,
Nb.sub.2O.sub.3, SiO.sub.2, Ta.sub.2O.sub.5, ThO.sub.2, TiO.sub.2,
Y.sub.2O.sub.3, ZrO.sub.2 and ZrSiO.sub.2,
Examples of the nitride used for the seed material layer 110
include: AlN, GaN, InN, BN, Be.sub.3N.sub.2, Cr.sub.2N, HfN, MoN,
NbN, Si.sub.3N.sub.4, TaN, Ta.sub.2N, Th.sub.2N.sub.2, TiN,
WN.sub.2, W.sub.2N, VN and ZrN.
Examples of the carbide used for the seed material layer 110
include: B.sub.4C, Cr.sub.2, HfC, LaC.sub.2, Mo.sub.2C, Nb.sub.2C,
SiC, Ta.sub.2C, ThC.sub.2, TiC, W.sub.2C, WC, V.sub.2C and ZrC,
Examples of the boride used for the seed material layer 110
include: AlB.sub.2, BeB.sub.2, CrB.sub.2, HfB.sub.2, LaB.sub.2,
MoB.sub.2, MoB, NbB.sub.4, SiB.sub.6, TaB.sub.2, ThB.sub.4,
TiB.sub.2, WB, VB.sub.2 and ZrB.sub.2.
Examples of the oxynitride used for the seed material layer 110
include AlON and SiON.
Examples of the carbonnitride used for the seed material layer 110
include SiCN,
Examples of the silicide used for the seed material layer 110
include: CrSi.sub.2, Cr.sub.2Si, HfSi.sub.2, MoSi.sub.2,
NbSi.sub.2, TaSi.sub.2, Ta.sub.5Si.sub.3, ThSi.sub.2,
Ti.sub.5Si.sub.3, WSi.sub.2, W.sub.5Si.sub.3, V.sub.3Si and
ZrSi.sub.2.
In exemplary embodiments, the seed material layer 110 is formed
through high-temperature/low temperature chemical vapor deposition
("CVD") using chemical reaction and/or physical vapor deposition
("PVD"), wherein the CVD includes metal-organic chemical vapor
deposition ("MOCVD") and plasma enhanced chemical vapor deposition
("PECVD"). The PVD includes thermal or E-beam evaporation, pulsed
laser deposition, sputtering deposition employing gas ions, such as
oxygen (O.sub.2), nitrogen (N.sub.2), or argon (Ar), and
co-sputtering deposition using at least two sputtering guns.
More preferably, the seed material layer 110 is deposited on the
upper surface of the first substrate 100 within a temperature range
between room temperature and 1500.degree. C.
According to another exemplary embodiment of the present invention,
instead of a single seed material layer 110 shown in FIG. 1A, first
and second seed material layers 110a and 110b are formed on the
first substrate 100 including sapphire, silicon (Si), zinc oxide
("ZnO") or gallium arsenide ("GaAs"). In this case, the
multifunctional substrate 120 is grown from the upper surface of
the second seed material layer 110b and the single-crystal
nitride-based layer or the light emitting structure 130 is stacked
on the multifunctional substrate 120.
If the seed material layer is prepared in the form of a bi-layer
structure as shown in FIG. 1B, the quality of the multifunctional
substrate 120 can be improved, thus improving the quality of the
single-crystal nitride-based layer or the light emitting structure
130.
In exemplary embodiments, the first seed material layer 110a
includes a material different from that of the second seed material
layer 110b.
FIGS. 2A and 2B are cross-sectional views showing a ZnO-based layer
240 formed on a first substrate 200, a seed material layer 210 in
the form of a single layer (FIG. 2A) or a bi-layer (FIG. 2B)
provided on the upper surface the ZnO-based layer 240, a
multifunctional substrate 220 formed on the seed material layer
210, and a single-crystal nitride-based layer 230 (or a light
emitting structure for a light emitting device) formed on the
multifunctional substrate 220 for the purpose of homoepitaxial
growth.
Referring to FIGS. 2A and 2B, after growing the single-crystal
nitride-based layer or the light emitting structure 230 by using
the seed material layer 210 in the form of a single layer or a
bi-layer and the multifunctional substrate 220, the ZnO-based layer
240, which is easily dissolved by means of acid and base solution,
is formed on the upper surface of the first substrate 200 before
the seed material layer 210 is deposited on the upper surface of
the first substrate 200 in such a manner that the thick first
substrate 200 can be readily removed through wet etching or dry
etching without causing any etching damage to the single-crystal
nitride-based layer or the light emitting structure 230.
At least one of silicon (Si), germanium (Ge), indium (In), lithium
(Li), gallium (Ga), magnesium (Mg), zinc (Zn), beryllium (Be),
molybdenum (Mo), vanadium (V), copper (Cu), iridium (Ir), rhodium
(Rh), ruthenium (Ru), tungsten (W), cobalt (Co), nickel (Ni),
manganese (Mn), titanium (Ti), tantalum (Ta), chrome (Cr), and
lanthanum (La) is added to the ZnO-based layer 240.
In exemplary embodiments, the amount of elements added to the
ZnO-based layer 240 is limited within a range of about 0.1 weight
percent to about 49 weight percent.
In exemplary embodiments, the ZnO-based layer 240 is formed through
high-temperature/low temperature chemical vapor deposition ("CVD")
using chemical reaction and/or physical vapor deposition ("PVD"),
wherein the CVD includes metal-organic chemical vapor deposition
("MOCVD") and plasma enhanced chemical vapor deposition ("PECVD").
The PVD includes thermal or E-beam evaporation, pulsed laser
deposition, sputtering deposition employing gas ions, such as
oxygen (O.sub.2), nitrogen (N.sub.2), or argon (Ar), and
co-sputtering deposition using at least two sputtering guns.
More preferably, the ZnO-based layer 240 is grown from the upper
surface of the first substrate 200 within a temperature range
between room temperature and 1500.degree. C.
FIG. 3 is a cross-sectional view showing a stacked structure in
which the ZnO-based layer and the seed material layer SML have been
removed.
Referring to FIG. 3, the thick first substrate 100 or 200, the
ZnO-based layer 240, and the seed material layer 110 or 210 are
completely removed from the stack structure shown in FIGS. 1 and 2
through performing wet etching by using acid solution or base
solution or performing dry etching by using gas ions, such as
hydrogen ions. The single-crystal nitride-based layer or the light
emitting structure 330 for the light emitting device is stacked on
the upper surface of the multifunctional substrate 320 for the
purpose of homoepitaxial growth.
In exemplary embodiments, in order to improve crystallinity or
electrical characteristics of the single-crystal nitride-based
layer or the light emitting structure 330 stacked on the upper
surface of the multifunctional substrate 320 for the purpose of
homoepitaxial growth, a heat-treatment process is performed within
a temperature range between room temperature and 1500.degree. C.
under oxygen (O.sub.2), nitrogen (N.sub.2), hydrogen (H.sub.2),
argon (Ar), vacuum or air atmosphere.
FIG. 4A is a flowchart showing the procedure of manufacturing a
vertical top emission type nitride-based light emitting device.
FIG. 4B is a cross-sectional view showing the vertical top emission
type nitride-based light emitting device including a ZnO-based
layer, a seed material layer SML, and a multifunctional substrate
MS according to an exemplary embodiment of the present
invention.
Referring to FIGS. 4A and 4B, similar to FIGS. 3A and 3B, a
nitride-based buffer layer 420 and a nitride-based light emitting
structure, which includes an n-nitride-based cladding layer 430, a
nitride-based active layer 440 and a p-nitride-based cladding layer
450, are sequentially formed on the upper surface of a
multifunctional substrate 410 at blocks 405, 415, 425, 435 and 445.
A second supporting substrate is attached to an upper portion of a
p-nitride-based semiconductor layer so as to prevent the light
emitting structure from being dissolved during the manufacturing
process for the nitride-based light emitting device at block 455.
Then, lithography and etching processes are performed so as to form
patterns having various sizes and intervals in the multifunctional
substrate 410 at blocks 465 and 475. In this state, a reflective
n-ohmic contact layer 480 is formed in the multifunctional
substrate 410 at block 485 and a metallic reflector 490 is
deposited on the bottom surface of the multifunctional substrate
410 at block 495. Thereafter, the second supporting substrate
attached to the upper portion of the p-nitride-based semiconductor
is removed and a transparent p-ohmic contact layer 460 is formed on
the p-nitride-based cladding layer 450 at block 505, thereby
obtaining the vertical top emission type nitride-based light
emitting device.
The procedure of manufacturing the high-quality light emitting
device by using the single-crystal nitride-based semiconductor
substrate according to the present invention may not be limited to
the procedure shown in FIG. 4A. In other words, the procedure shown
in FIG. 4A can be modified in combination with technologies
suitable to fabricate the highly reliable light emitting device
used as a next-generation white light source.
According to another exemplary embodiment of the present invention,
the seed material layer SML including chrome oxide
("Cr.sub.2O.sub.3") is deposited on the upper surface of the first
substrate FS including sapphire, silicon (Si), silicon germanium
("SiGe"), zinc oxide ("ZnO") or gallium arsenide ("GaAs"), and the
multifunctional substrate MS 410 including single-crystal aluminum
oxide (Al.sub.2O.sub.3) is grown from the upper surface of the seed
material layer SML. In this state, the nitride-based buffer layer
420 and the single-crystal nitride-based light emitting structure,
which includes the n-nitride-based cladding layer 430, the
nitride-based active layer 440 and the p-nitride-based cladding
layer 450, are sequentially stacked on the multifunctional
substrate MS, thereby obtaining the vertical top emission type
nitride-based light emitting device according to the present
invention.
In general, each of the nitride-based buffer layer 420, the
n-nitride-based cladding layer 430, the nitride-based active layer
440 and the p-nitride-based cladding layer 450 basically include a
compound selected from Group III nitride-based compounds expressed
as AlxInyGazN (where x, y and z are integers). In addition, dopant
is added to the n-nitride-based cladding layer 430 and the
p-nitride-based cladding layer 450.
The nitride-based active layer 440 can be prepared in the form of a
single layer or a multiple quantum well ("MQW"), that is, a
bi-layer such as an AlxInyGazN/AlxInyGazN layer (where x, y and z
are integers).
If a GaN-based compound is used to fabricate the nitride-based
light emitting device, the nitride-based buffer layer 420 is formed
by using GaN, the n-nitride-based cladding layer 430 is formed by
adding n-dopant, such as silicon (Si), germanium (Ge), selenium
(Se) or tellurium (Te), to GaN, the nitride-based active layer 440
is prepared in the form of InGaN/GaN MQW or AlGaN/GaN MQW. The
p-nitride-based cladding layer 450 is formed by adding p-dopant,
such as magnesium (Mg), zinc (Zn), calcium (Ca), strontium (St) or
barium (Ba), to GaN.
The reflective n-ohmic contact layer 480 is interposed between the
n-nitride-based cladding layer 430 and the metallic reflector 490.
The reflective n-ohmic contact layer 480 may have various
structures generally known in the art, such as an aluminum/titanium
(Al/Ti) layer having a large thickness. In exemplary embodiments,
the metallic reflector 490 includes a thick reflective metal, such
as aluminum (Al), silver (Ag) or rhodium (Rh).
The transparent p-ohmic contact layer 460 includes electrode
materials used to form a p-ohmic contact. The electrode materials
include oxidized nickel-gold ("Ni--Au"), oxidized silver (Ag),
transparent conducting oxides, which are oxide compounds based on
indium tin oxide ("ITO"), zinc oxide ("ZnO"), tin oxide
("SnO.sub.2"), or indium oxide ("In.sub.2O.sub.3"), and conducting
transitional metal nitrides including tin nitrides ("TiN"). In
addition, a p-electrode pad 470 has a stacked layer structure, such
as a nickel/gold ("Ni/Au") layer or a silver/gold (Ag/Au)
layer.
The above layers can be formed through conventional deposition
methods, such as E-beam evaporation, physical vapor deposition
("PVD"), chemical vapor deposition ("CVD"), plasma laser deposition
("PLD"), dual-type thermal evaporation, orsputtering.
FIG. 5A is a flowchart showing a procedure of manufacturing a
vertical flip chip type nitride-based light emitting device. FIG.
5B is a cross-sectional view showing the vertical flip chip type
nitride-based light emitting device including a ZnO-based layer, a
seed material layer SML and a multifunctional substrate according
to an exemplary embodiment of the present invention.
Referring to FIGS. 5A and 5B, similar to FIGS. 3A and 3B, a
nitride-based buffer layer 520 and a nitride-based light emitting
structure, which includes an n-nitride-based cladding layer 530, a
nitride-based active layer 540 and a p-nitride-based cladding layer
550, are sequentially formed on the upper surface of a
multifunctional substrate 510 at blocks 515, 525, 535, 545 and 555.
After that, a second supporting substrate is attached to an upper
portion of a p-nitride-based semiconductor layer so as to prevent
the light emitting structure from being dissolved during the
manufacturing process for the nitride-based light emitting device
at block 565. Then, lithography and etching processes are performed
so as to form patterns having various sizes and intervals in the
multifunctional substrate 510 at blocks 575 and 585. In this state,
a transparent n-ohmic contact layer 580 is formed in the
multifunctional substrate 510 at block 595 and a transparent
conducting layer 490 is deposited on the bottom surface of the
multifunctional substrate 510 at block 605. Thereafter, the second
supporting substrate attached to the upper portion of the
p-nitride-based semiconductor is removed at block 615 and a
reflective p-ohmic contact layer 560 is formed on the
p-nitride-based cladding layer 550 at block 625, thereby obtaining
the vertical flip chip type nitride-based light emitting
device.
The procedure of manufacturing the high-quality light emitting
device by using the single-crystal nitride-based semiconductor
substrate according to the present invention may not be limited to
the procedure shown in FIG. 5A. In other words, the procedure shown
in FIG. 5A can be modified in combination with technologies
suitable to fabricate the highly reliable light emitting device
used as a next-generation white light source.
According to an exemplary embodiment of the present invention, the
seed material layer SML including zinc oxide ("ZnO") or molybdenum
(Mo) is deposited on the upper surface of the first substrate FS
including sapphire, silicon (Si), silicon germanium ("SiGe"), zinc
oxide ("ZnO") or gallium arsenide ("GaAs"), and the multifunctional
substrate MS including single-crystal aluminum oxide
("Al.sub.2O.sub.3") is grown from the upper surface of the seed
material layer SML. In this state, the nitride-based buffer layer
520 and the single-crystal nitride-based light emitting structure,
which includes the n-nitride-based cladding layer 430, the
nitride-based active layer 440 and the p-nitride-based cladding
layer 450, are sequentially stacked on the multifunctional
substrate MS, thereby obtaining the vertical flip chip type
nitride-based light emitting device according to the present
invention.
In general, each of the nitride-based buffer layer 520, the
n-nitride-based cladding layer 530, the nitride-based active layer
540 and the p-nitride-based cladding layer 550 basically include a
compound selected from Group III nitride-based compounds expressed
as AlxInyGazN (where x, y and z are integers). In addition, dopant
is added to the n-nitride-based cladding layer 530 and the
p-nitride-based cladding layer 550.
The nitride-based active layer 540 can be prepared in the form of a
single layer or a multiple quantum well ("MQW"), that is, a
bi-layer such as an AlxInyGazN/AlxInyGazN layer (where x, y and z
are integers).
If a GaN-based compound is used to fabricate the nitride-based
light emitting device, the nitride-based buffer layer 520 is formed
by using GaN, the n-nitride-based cladding layer 530 is formed by
adding n-dopant, such as silicon (Si), germanium (Ge), selenium
(Se) or tellurium (Te), to GaN, the nitride-based active layer 540
is prepared in the form of InGaN/GaN MQW or AlGaN/GaN MQW. The
p-nitride-based cladding layer 550 is formed by adding p-dopant,
such as magnesium (Mg), zinc (Zn), calcium (Ca), strontium (St) or
barium (Ba), to GaN.
The transparent n-ohmic contact layer 580 is interposed between the
n-nitride-based cladding layer 530 and the transparent conducting
layer 590. The transparent n-ohmic contact layer 580 includes
electrode materials used to form a p-ohmic contact. The electrode
materials include transparent conducting oxides, which are oxide
compounds based on indium tin oxide ("ITO"), zinc oxide ("ZnO"),
tin oxide ("SnO.sub.2"), or indium oxide ("In.sub.2O.sub.3"), and
conducting transitional metal nitrides including tin nitrides
("TiN"). In addition, the transparent conducting layer 590 is
formed by using conducting transitional metal nitrides including
tin nitrides ("TiN") or transparent conducting oxides, which are
oxide compounds based on indium tin oxide ("ITO"), zinc oxide
("ZnO"), tin oxide ("SnO.sub.2"), or indium oxide
("In.sub.2O.sub.3").
The reflective p-ohmic contact layer 560 includes electrode
materials used to form a reflective p-ohmic contact, such as
aluminum (Al), silver (Ag) or rhodium (Rh), which is generally
known in the art. In addition, a p-electrode pad 570 has a stacked
layer structure, such as a nickel/gold ("Ni/Au") layer or a
silver/gold ("Ag/Au") layer.
The above layers can be formed through conventional deposition
methods, such as E-beam evaporation, physical vapor deposition
("PVD"), chemical vapor deposition ("CVD"), plasma laser deposition
("PLD"), dual-type thermal evaporation, or sputtering.
FIG. 6A is a flowchart showing a procedure of manufacturing a
vertical top emission type nitride-based light emitting device.
FIG. 6B is a cross-sectional view showing the vertical top emission
type nitride-based light emitting device including a ZnO-based
layer, a seed material layer SML and a multifunctional substrate
according to another exemplary embodiment of the present
invention.
Referring to FIGS. 6A and 6B, similar to FIGS. 3A and 3B, a
nitride-based buffer layer and a nitride-based light emitting
structure, which includes an n-nitride-based cladding layer 650, a
nitride-based active layer 640 and a p-nitride-based cladding layer
630, are sequentially formed on the upper surface of a
multifunctional substrate MS at blocks 635, 645, 655, 665 and 675.
After that, a second supporting substrate is attached to an upper
portion of a p-nitride-based semiconductor layer at block 685 to
prevent the light emitting structure from being dissolved during
the manufacturing process for the nitride-based light emitting
device. Then, the multifunctional substrate MS is completely
removed through the wet etching process or the dry etching process
at blocks 695 and 705, and a reflective bonding p-ohmic contact
layer 620 (e.g., third supporting substrate) is bonded to a first
supporting substrate 610 by means of a bonding material at block
715. Thereafter, the second supporting substrate attached to the
upper portion of the p-nitride-based semiconductor is removed at
block 725 and a transparent n-ohmic contact layer 660 is formed on
the n-nitride-based cladding layer 650 at block 735, thereby
obtaining the vertical top emission type nitride-based light
emitting device.
The procedure of manufacturing the high-quality light emitting
device by using the single-crystal nitride-based semiconductor
substrate according to the present invention may not be limited to
the procedure shown in FIG. 6A. In other words, the procedure shown
in FIG. 6A can be modified in combination with technologies
suitable to fabricate the highly reliable light emitting device
used as a next-generation white light source.
According to the exemplary embodiment of the present invention, the
seed material layer SML including zinc oxide ("ZnO") or titanium
(Ti) is deposited on the upper surface of the first substrate FS
including sapphire, silicon (Si), silicon germanium ("SiGe"), zinc
oxide ("ZnO") or gallium arsenide ("GaAs"), and the multifunctional
substrate MS including single-crystal aluminum oxide
("Al.sub.2O.sub.3") is grown from the upper surface of the seed
material layer SML. In this state, the nitride-based buffer layer
and the single-crystal nitride-based light emitting structure,
which includes the n-nitride-based cladding layer 650, the
nitride-based active layer 640 and the p-nitride-based cladding
layer 630, are sequentially stacked on the multifunctional
substrate MS 620, thereby obtaining the vertical top emission type
nitride-based light emitting device according to the present
invention.
In general, each of the nitride-based buffer layer, the
n-nitride-based cladding layer 650, the nitride-based active layer
640 and the p-nitride-based cladding layer 630 basically include a
compound selected from Group III nitride-based compounds expressed
as AlxInyGazN (where x, y and z are integers). In addition, dopant
is added to the n-nitride-based cladding layer 650 and the
p-nitride-based cladding layer 630.
The nitride-based active layer 640 can be prepared in the form of a
single layer or a multiple quantum well ("MQW"), that is, a
bi-layer such as an AlxInyGazN/AlxInyGazN layer (where x, y and z
are integers).
If a GaN-based compound is used to fabricate the nitride-based
light emitting device, the nitride-based buffer layer is formed by
using GaN, the n-nitride-based cladding layer 650 is formed by
adding n-dopant, such as silicon (Si), germanium (Ge), selenium
(Se) or tellurium (Te), to GaN, the nitride-based active layer 640
is prepared in the form of InGaN/GaN MQW or AlGaN/GaN MQW, and the
p-nitride-based cladding layer 630 is formed by adding p-dopant,
such as magnesium (Mg), zinc (Zn), calcium (Ca), strontium (St) or
barium (Ba), to GaN.
The transparent n-ohmic contact layer 660 is interposed between the
n-nitride-based cladding layer 650 and a reflective n-electrode pad
670. The transparent n-ohmic contact layer 660 includes electrode
materials used to form a p-ohmic contact. The electrode materials
include transparent conducting oxides, which are oxide compounds
based on indium tin oxide ("ITO"), zinc oxide ("ZnO"), tin oxide
("SnO.sub.2"), or indium oxide ("In.sub.2O.sub.3"), and conducting
transitional metal nitrides including tin nitrides ("TiN"). In
addition, the reflective n-electrode pad 670 has a stacked layer
structure, such as a nickel/gold ("Ni/Au") layer or a silver/gold
("Ag/Au") layer. The reflective bonding p-ohmic contact layer 620
can be formed with various structures having a large thickness by
using a solid solution or a reflective metal, such as silver (Ag)
or rhodium (Rh).
The above layers can be formed through conventional deposition
methods, such as E-beam evaporation, physical vapor deposition
("PVD"), chemical vapor deposition ("CVD"), plasma laser deposition
("PLD"), dual-type thermal evaporation, orsputtering.
As described above, the present invention provides a single-crystal
nitride-based semiconductor substrate and a method of manufacturing
a vertical type nitride-based light emitting device by using the
same. According to the present invention, a single-crystal
nitride-based semiconductor substrate or a light emitting structure
for homoepitaxial growth can be formed under high temperature and
hydrogen atmosphere by using a seed material layer SML and a
multifunctional substrate MS, which are sequentially formed on an
upper surface of a first substrate FS so as to prevent mechanical
and thermal strain and decomposition from occurring at the upper
surface of the first substrate FS including sapphire, silicon (Si),
zinc oxide ("ZnO") or gallium arsenide ("GaAs"). Thus, the present
invention provides a high-quality nitride-based light emitting
device representing superior light efficiency and heat dissipation
while being operated at a low operational voltage.
Although the exemplary embodiments of the present invention have
been described, it is understood that the present invention should
not be limited to these exemplary embodiments but various changes
and modifications can be made by one ordinary skilled in the art
within the spirit and scope of the present invention as hereinafter
claimed.
* * * * *